Recently, image diagnosis using a medical image diagnostic apparatus typified by an ultrasonic diagnostic apparatus, X-ray computed tomography apparatus, magnetic resonance imaging apparatus, and the like has an important role in clinical fields. For example, an ultrasonic diagnostic apparatus is an apparatus which applies ultrasonic pulses generated by the transducers provided in an ultrasonic probe into an object to be examined, and receives reflected ultrasonic waves generated by differences in acoustic impedance of the tissues of the object via the transducers, thereby acquiring biological information. This apparatus can perform real-time display of image data by the simple operation of bringing the ultrasonic probe into contact with the surface of the body, and hence is widely used for morphological diagnosis and functional diagnosis of various organs.
Recently, a system capable of high-speed acquisition and display of three-dimensional images has been rapidly developed, and hence has become capable of providing diagnostic images in different fields of view such as three-dimensional images and three-dimensional moving images.
On the other hand, image diagnosis using an ultrasonic diagnostic apparatus is image diagnosis using ultrasonic waves propagating in the living body. Even if, therefore, this apparatus is made compatible to three-dimensional images, there is a certain limitation on the number of scanning lines which the apparatus can transmit/receive per unit time. For this reason, various techniques have been attempted to scan a wide three-dimensional area with high resolution. When visualizing a wide region by using an ultrasonic diagnostic apparatus, the apparatus basically generates a three-dimensional image in a wide range by concatenating image data obtained by scanning three-dimensional spaces in small areas.
When, however, acquiring living body images, since some regions move due to respirations and the pulsations of the heart, it is necessary to acquire three-dimensional images in synchronism with these movements.
There is known a recently employed method of acquiring a plurality of small area three-dimensional moving images in synchronism with the movement of the heart and generating a three-dimensional moving image of the overall heart by combining the images. Such a method acquires and combines a plurality of small area three-dimensional moving images in synchronism with the movement of the heart. For example, image acquisition is often performed in synchronism with the movement of the heart by using biological signals such as ECG signals.
More specifically, this method divides the overall three-dimensional area of the heart to be observed with an ultrasonic diagnostic apparatus into a plurality of sub-volumes (e.g., four sub-volumes), and sequentially acquires data corresponding to one heartbeat concerning each sub-volume based on an ECG signal. In this data acquisition, for example, the method acquires data in the same time phases in a heartbeat cycle with reference to a position near an end-diastole at which an R wave is generated. The method then generates data corresponding to the three-dimensional area by combining the respective acquired sub-volume data so as to make the data in the same time phases spatially continuous.
Although each sub-volume corresponds to each area obtained by dividing a three-dimensional space, reconstructing data corresponding to spatially continuous three-dimensional areas can provide a three-dimensional image (to be referred to as a three-dimensional area moving image hereinafter) which looks as if moving images of the overall three-dimensional area of the heart to be observed were collected and displayed at once.
When using the above method, in order to visually recognize the three-dimensional area moving image obtained by combining the data of the respective sub-volumes as a single three-dimensional moving image, the respective sub-volumes need to be spatially continuous sub-volumes, and it is necessary to acquire data in the same time phases.
If, however, an object is, for example, an arrhythmic patient, when the heartbeat cycle is disturbed, the heartbeat period changes. As a consequence, the time phases of data acquired concerning the respective sub-volumes shift from each other. This makes it difficult to obtain a practical three-dimensional area moving image.
This embodiment has been made in consideration of the above problem, and has as its object to provide an ultrasonic diagnostic apparatus, ultrasonic image processing apparatus, and medical image diagnostic apparatus which present a three-dimensional area moving image obtained by combining data in the same time phases for the respective sub-volumes even if the heartbeat cycle or heartbeat period is disturbed as in a case in which, for example, an object is an arrhythmic patient.